title: Anion reduction dominated cathodic limit of metal-free ionic liquid: experimental and theoretical proofs.
abstract: The cathodic limit of the electrochemical window in the second-generation ionic liquids (composed of air- and water-stable metal-free cations and anions) is traditionally believed to be determined by the reduction of the cation. More and more exceptions, however, were found in various ionic liquids. In this study, the cathodic limit of the electrochemical window in 1-butyl-1-methylpyrrolidinium salicylate ionic liquid (BMP-SAL IL) was studied. It has been found that the cathodic limit of BMP-SAL is determined by the reduction of SAL(-) anion rather than the reduction of BMP(+) cation. The cyclic voltammetric behavior, NMR spectra, and MALDI-TOF MS spectra of BMP-SAL recorded before and after the IL was electrolyzed at the cathodic limit provide sufficient evidence that the major reaction at the cathodic limit of BMP-SAL is the reduction of SAL(-) anion. The theoretical calculations support the experimental data, and the results indicate that anion reduction dominated cathodic limit should be a common phenomenon in ionic liquids.
authors.affiliation: Department of Medicinal and Applied Chemistry, Kaohsiung Medical University , Kaohsiung 807, Taiwan.
authors.forename: Nai-Chang
authors.initials: NC
authors.lastname: Lo
authors.forename: Hsing-Yin
authors.initials: HY
authors.lastname: Chen
authors.forename: Wan-Jung
authors.initials: WJ
authors.lastname: Chuang
authors.forename: Chi-Yu
authors.initials: CY
authors.lastname: Lu
authors.forename: Ping-Yu
authors.initials: PY
authors.lastname: Chen
authors.forename: Po-Yu
authors.initials: PY
authors.lastname: Chen
mesh_terms: D000838:Anions / Q000737:chemistry; D055664:Electrochemical Techniques; D004566:Electrodes; D052578:Ionic Liquids / Q000737:chemistry*; D008670:Metals / Q000737:chemistry*; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D011789:Quantum Theory; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000838:Anions; D052578:Ionic Liquids; D008670:Metals